Influence of humidity on the gas sensing characteristics of SnO2

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There is a growing demand for devices that can detect small concentrations of gases for various applications, such as leakage detection in industrial processes, mobile phones, and automated ventilation systems. Sensors utilizing Semiconducting Metal Oxides (SMOX), particularly SnO2, present an inexpensive and robust solution. However, the sensing process of SnO2 is not yet fully understood, particularly how humidity affects its operation in relevant conditions. This study focuses on this aspect by investigating four different SnO2 materials, representing a broad range of SnO2 types. The research examines their sensing performance towards CO, EtOH, CH4, and H2 under varying humidity levels using DC resistance, catalytic conversion, and Diffuse Reflectance Infrared Fourier Spectroscopy (DRIFTS) measurements. Findings indicate that water does not always act as a reducing gas on all SnO2 materials, as previously reported; it can also react in an electroneutral manner. Additionally, the effects of Cobalt and Palladium doping on selectivity and sensor signals were thoroughly explored. The insights gained regarding the sensing characteristics and mechanisms of SnO2 provide a foundational toolbox for future sensor development.